Transmission level control method and transceiver apparatus in wireless local loop system

ABSTRACT

A transmission level control method in a wireless local loop system capable of suppressing occurrence of an unnecessarily high transmission level, comprises a step of generating a required reception level corresponding to a classification of data, a step of detecting the reception level of data at a receiver side transceiver apparatus, a step of finding a level difference between the detected reception level and the required reception level corresponding to the classification of the related received data, and a step of controlling a change of the transmission level at a transmitter side transceiver apparatus according to this level difference.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of and claims priority under35 USC § 120 from U.S. patent application Ser. No. 09/394,499, filed onSep. 13, 1999, now U.S. Pat. No. 6,829,488 which claims priority under35 USC § 119 from Japanese Patent Application Number 10-269741 filed onSep. 24, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transceiver apparatus in a wirelesslocal loop system, more particularly relates to transmission levelcontrol in the transceiver apparatus.

In recent years, due to the rapid advances being made in datacommunications technology and the accompanying improvement and reductionof price of the data communications apparatuses such as personalcomputers etc., there has been a rapid spread of use of multimediaapplications through the Internet. In the future, there are expected tobe a variety of applications using the Internet etc. such as remoteeducation and medical treatment and increasing electronic commercialtransactions. Under these circumstances, an increase of the speed ofnetworks, an enlargement of their capacity, and a reduction of theircosts are being urgently sought worldwide. In Japan, the government hasproposed establishment of a nation-wide optical fiber network reachinginto every home (FTTH: Fiber To The Home) aimed at completion by theyear 2010. However, the year 2010 is still far in the future. On theother hand, some claim that it would be difficult to lay optical fibersto all homes even by the year 2010 and that the most that could beaccomplished would be laying optical fibers reaching individualcommunities (FTTC: Fiber To The Curb).

In view of the above, interest is now focusing on establishment ofwireless local loop systems for providing high speed, large capacityservice to individual homes by wireless channels. The Japanese Ministryof Posts and Telecommunications and other leading agencies have set up astudy group and have set targets for commercialization. The presentinvention relates to such a wireless local loop system. In particular,it relates to a system for controlling the transmission level in adigital radio transceiver apparatus in a wireless local loop system fortime division multiplex transmission of various types of data. Itdescribes a method for transmission level control on a same channeltaking into consideration a reception level at an opposing side and arequired reception level differing for every classification of data tobe transmitted.

2. Description of the Related Art

As will be explained in detail later by using the drawings, a wirelesslocal loop system performs the transmission and reception of informationvia a radio transmission path between a first transceiver apparatus anda second transceiver apparatus.

When desiring to transmit a variety of data having different requiredcarrier-to-noise (C/N) ratios and bit error rates (BER) for eachsubscriber as in a wireless local loop system, the lines are designed tomatch with the strictest required C/N on the same channel and thetransmission level of the related channel is determined accordingly inmultiplex channels of trunk line networks and repeater networks and inATM communications. Accordingly, when transmitting data not having astrict required C/N condition, there is the problem that thetransmission will be carried out with an excessive output.

SUMMARY OF THE INVENTION

In consideration with the above problem, an object of the presentinvention is to provide a transmission level control method and atransceiver apparatus in a wireless local loop system enablingtransmission level control on a same channel by referring to thereception level and BER and further taking into account theclassification of the transmission data—without distinguishing whetherthe data is continuous or discontinuous—for suppressing the aboveexcessive level of transmission output and, accordingly, lowering thepower consumption and reducing the interference to other channels.

To attain the above object, the method of the present invention is atransmission level control method capable of suppressing the occurrenceof an unnecessarily high transmission level in a wireless local loopsystem. This method comprises a step of generating required receptionlevels corresponding to respective classifications of data, a step ofdetecting the reception level of data in a receiver side transceiverapparatus, a step of finding a level difference between the detectedreception level and the required reception level corresponding to theclassification of the related received data, and a step of controlling achange, i.e., increase and decrease, of the transmission level in atransmitter side transceiver apparatus according to this leveldifference.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object and features of the present invention will be moreapparent from the following description of the preferred embodimentsgiven with reference to the accompanying drawings, wherein:

FIG. 1 is a view of the basic steps of a transmission level controlmethod according to the present invention;

FIG. 2 is a flow chart showing the steps shown in FIG. 1 moreconcretely;

FIG. 3 is a block diagram of a first embodiment of first and secondtransceiver apparatuses according to the present invention;

FIG. 4 is a block diagram of a second embodiment of first and secondtransceiver apparatuses according to the present invention;

FIG. 5 is a view of a first example for generating a required receptionlevel;

FIG. 6 is a view of a second example for generating a required receptionlevel.

FIG. 7 is a view of a third example for generating a required receptionlevel;

FIG. 8 is a view of a fourth example for generating a required receptionlevel;

FIG. 9 is a view of a fifth example for generating a required receptionlevel;

FIG. 10 is a view of a sixth example for generating a required receptionlevel;

FIG. 11 is a view of a seventh example for generating a requiredreception level;

FIG. 12 is a view of an eighth example for generating a requiredreception level;

FIG. 13 is a view for explaining adjustment in the case of generatingthe required reception level; and

FIG. 14 is a view diagrammatically illustrating the concept of awireless local loop system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the embodiments of the present invention, the relatedart and the disadvantages therein will be described with reference tothe related figures.

FIG. 14 is a view diagrammatically illustrating the concept of awireless local loop system.

In the figure, reference numeral 10 indicates a wireless local loopsystem which performs the transmission and reception of information viaa radio transmission path 15 between a first transceiver apparatus 11and a second transceiver apparatus 12.

The first transceiver apparatus 11 is provided in for example a basetransceiver station 13. Further, a second transceiver apparatus 12 isprovided in for example each subscriber's home 14. In the followingexplanation, however, it is also possible to consider the firsttransceiver apparatus 11 being provided in each subscriber's home 14,and the second transceiver apparatus 12 being provided in the basetransceiver station 13.

Note that the base transceiver station 13 is connected to a publicswitch telephone network (PSTN) via a radio link (RL) or an opticalfiber (OF).

Since it is becoming important to avoid interference with other channelsalong with the spread of wireless local loop systems and since it isdesirable to lower the power consumption, it becomes indispensable totransmit the data with the required lowest limit output capable ofsecuring a channel quality.

Further, due to an attenuation by rain, and multipath fading or thelike, also the reception level at the opposing side varies, so thecontrol of the transmission level is important, and a variety of controlmethods have been proposed also in the past.

However, in the transmission level control method on multiplex channelsof the repeater network and trunk line network of the related art, itwas a method of realizing the control of the required lowest limittransmission level by monitoring the reception level at opposing side orBER (Bit Error Rate) or the like, or a method of transmitting aplurality of transmission information having different required BER, forexample a header part and a data part of a cell by a plurality ofchannels in the ATM communication, and individually performing the powercontrol, or another method.

Here, in the wireless local loop system, there is an already mentionedproblem for the transmission level control. Namely, it is the followingproblem: Where it is intended to transmit a variety of data havingdifferent required C/N (Carrier/Noise) and Bit Error Rate (BER) for eachsubscriber as in the wireless local loop system, in multiplex channelsof trunk line network and repeater network, and in ATM communications,on the same channel, the design of line is carried out so as to matchwith the strictest required C/N, and the transmission level of therelated channel is determined. Accordingly, at the transmission of thedata not having a strict required C/N condition, the transmission willbe carried out with an excessive output.

The present invention provides a transmission level control method and atransceiver apparatus in a wireless local loop system enablingtransmission level control on a same channel by referring to thereception level and BER and further taking into account theclassification of the transmission data—without distinguishing whetherthe data is continuous or discontinuous—for suppressing an excessivelevel of transmission output and accordingly lowering the powerconsumption and reducing the interference to other channels.

Since bit error cannot be avoided on a radio transmission path, thelines are designed according to a prescribed standard concerning biterror. The larger the degree of information compression, the larger theeffect of the bit error is believed to be. The values of BER generallygiven as rough standards are shown in the following Table 1 (values ofBER corresponding to data classifications).

TABLE 1 Data classification BER Video 3 × 10⁻⁹ Teletext broadcasting 1 ×10⁻⁸ Audio 4 × 10⁻⁶ Facsimile 1 × 10⁻⁵

Here, if the modulation system is the same for all of the dataclassifications, there is a one-to-one correspondence of the requiredC/N to the BER of the above Table 1. Due to this, by designing the linesusing the required C/N satisfying the BER required for each dataclassification, it becomes possible to secure a sufficient channelquality for each data classification. That is, if the modulation systemis the same, both the required C/N and the required reception level aredetermined in a one-to-one correspondence with respect to the BER foreach data classification.

Therefore, in the present invention, the reception level at the opposingside is detected, the value of the reception level and the requiredreception level corresponding to the classification of the data to betransmitted are compared, and the change, i.e., increase and decrease,of the transmission level is controlled in accordance with the leveldifference between the two levels. Summarizing this, the transmissionlevel is made larger for data with a low required BER (video or otherdata not allowing error), while the transmission level is made small fordata with a high required BER (facsimile or other data allowing error).

FIG. 1 is a view of the basic steps of the method of transmission levelcontrol according to the present invention.

The method according to the present invention provides a wireless localloop system for performing the transmission of data between onetransceiver apparatus and another transceiver apparatus through a radiotransmission path comprising the steps illustrated, that is,

Step S1: The required reception level (refer to the above Table 1)corresponding to the classification of data is generated.

Step S2: The reception level of the data in the receiver sidetransceiver apparatus (11 or 12) is detected.

Step S3: The detected reception level and the required reception levelcorresponding to the classification of the related received data arecompared, and the level difference between the two reception levels isfound.

Step S4: The change of the transmission level in the transmitter sidetransceiver apparatus (12 or 11) is controlled according to the leveldifference.

FIG. 2 is a flow chart showing the steps shown in FIG. 1 moreconcretely.

Referring to this figure, first, when receiving data, it isdiscriminated what the classification of the data to be transmitted is(<1> of FIG. 2, discrimination of classification of data).

A reception level enough to secure the channel quality is generatedbased on the required BER (Table 1) corresponding to the discriminatedclassification of data (<2> of FIG. 2, generation of the requiredreception level).

The reception level is detected by measuring the reception level of thedata at the receiver side transceiver apparatus. The detected receptionlevel and the required reception level are compared. When the receptionlevel is lower than the required reception level, the amount ofinsufficiency of the transmission level is increased. Conversely, whenthe transmission level is excessive, control is performed to maintainthe transmission level as it is or decrease the amount of excess etc.(<3> of FIG. 2, control of transmission level).

FIG. 3 is a block diagram of a first embodiment of the first and secondtransceiver apparatuses according to the present invention. First, whenlooking at the transceiver apparatus 11 at the left side of the figure,this is a transceiver apparatus 11 in a wireless local loop system 10for performing transferring data via a radio transmission path 15 andcomprises a required reception level generation part 21, a receptionlevel acquisition part 22, a comparison part 23, and a transmissionlevel control part 24.

The required reception level generation part 21 discriminates theclassification of the data, and generates the required reception levelcorresponding to this.

The reception level acquisition part 22 acquires the reception level ofthe data in the opposing side transceiver apparatus 12 via the radiotransmission path 15.

The comparison part 23 compares the required reception level and theacquired reception level and outputs the level difference of the two.

The transmission level control part 24 controls a change of thetransmission level of the data to the opposing side transceiverapparatus 12 according to the level difference.

On the other hand, when viewing the transceiver apparatus 12 on theright side of FIG. 3, this is also a transceiver apparatus 12 in awireless local loop system 10 for transferring data via a radiotransmission path 15 and comprises a reception part 26, a transmissionpart 27, and a reception level detection part 28.

The reception part 26 receives the data transmitted from the opposingside transceiver apparatus 11.

The transmission part 27 transmits the data to the opposing sidetransceiver apparatus 11.

The reception level detection part 28 detects the reception level of thedata received at the reception part 26.

Here, the transmission part 27 transmits the reception level informationindicative of that detected reception level to the opposing sidetransceiver apparatus 11 via the radio transmission path 15.

Explaining this in a little more detail along with FIG. 3, at thetransceiver apparatus 12 serving as the opposing side of the transceiverapparatus 11, at a receiver 41, a level measurement unit 43 measures thereception level and a transmitter 44 adds the reception levelinformation to data B to be transmitted to the transceiver apparatus 11and then transmits it via a duplexer 42. At the transceiver apparatus11, based on the data classification of data A to be transmitted, arequired reception level generation unit 34 generates the requiredreception level serving as the standard capable of securing the requiredBER. A comparison unit 35 compares this required reception level and thereception level information from the transceiver apparatus 12 obtainedat an opposing side reception level extraction unit 36 via a duplexer 32and a receiver 37. When the reception level is lower than the standardvalue, the transmission level is increased by exactly the insufficientamount, while conversely when it exceeds it, the transmission levelchange unit 33 performs control to maintain the transmission level as itis or decrease it by exactly the amount of excess.

Thus, in the first embodiment based on the present invention, thetransmission level is controlled in accordance with the following steps:

First step: Reception level information indicative of the receptionlevel of the data (data A) received at the opposing side transceiverapparatus 12 is received.

Second step: The reception level indicated in the received receptionlevel information and the required reception level corresponding to thediscriminated classification of the data (data A) to be transmitted tothe opposing side transceiver apparatus 12 are compared.

Third step: The change of the transmission level of the data (data A) tobe transmitted from the transceiver apparatus 11 is controlled accordingto the result of comparison.

FIG. 4 is a block diagram of a second embodiment of the first and secondtransceiver apparatuses according to the present invention. First, whenviewing the transceiver apparatus 12 on the right side of the figure,this is a transceiver apparatus 12 in a wireless local loop system 10for transferring data via a radio transmission path 15 and comprises arequired reception level generating part 51, a reception level detectionpart 52, a comparison part 53, and a transmission level changeinformation adding part 54.

The required reception level generating part 51 discriminates theclassification of the data received from the opposing side transceiverapparatus 11 and generates a required reception level corresponding tothis.

The reception level detection part 52 detects the reception level of thereceived data.

The comparison part 53 compares the required reception level and thedetected reception level and outputs the level difference of the two.

The transmission level change information adding part 54 adds thetransmission level change information according to the level differenceto the data to be transmitted to the opposing side transceiver apparatus11.

On the other hand, when viewing the transceiver apparatus 11 on the leftside of FIG. 4, this is also a transceiver apparatus 11 in a wirelesslocal loop system 10 for transferring data via a radio transmission path15 and comprises a reception part 56, a transmission part 57, and atransmission level control part 58.

The reception part 56 receives the data transmitted from the opposingside transceiver apparatus 12 together with the transmission levelchange information added to this data.

The transmission part 57 transmits the data to the opposing sidetransceiver apparatus 12.

The transmission level control part 58 controls the change of thetransmission level of the data to the opposing side transceiverapparatus 12 according to the transmission level change informationextracted from the reception part 56.

Note that, in FIG. 4, components performing the same functions as thoseof the components shown in FIG. 3 are indicated by the same referencenumerals. Explaining this in a little more detail along with FIG. 4, atthe transceiver apparatus 12 serving as the opposing side of thetransceiver apparatus 11, the comparison unit 35 compares the requiredreception level generated based on the data classification of thereceived data A and the reception level measured via the reception levelmeasurement unit 43 from the receiver 41 and prepares transmission levelchange information based on the result of the comparison. For example,when the reception level is lower than the standard reception level,information indicative of the amount of increase of the transmissionlevel based on the level difference is added to the data B to betransmitted to the transceiver apparatus 11. Conversely, when thereception level exceeds the standard reception level, informationindicative of maintaining the transmission level as it is or the amountof decrease of the transmission level for decreasing the amount ofexcess is added to the data B and transmitted. In the transceiverapparatus 11, the transmission level is controlled at the transmitter 31based on the transmission level change information. This control isperformed by the transmission level change unit 33.

Thus, in the second embodiment according to the present invention, thetransmission level is controlled in accordance with the following steps.

First step: The classification of the data (data A) received at thetransceiver apparatus 12 is discriminated and the required receptionlevel corresponding to this is generated.

Second step: The reception level of the data (data A) received at thetransceiver apparatus 12 is detected.

Third step: The required reception level and the detected receptionlevel are compared, and the level difference of the both is output.

Fourth step: The transmission level change information according to thelevel difference is added to the data (data B) to be transmitted fromthe transceiver apparatus 12.

Fifth step: The change of the transmission level of the data (data A) atthe opposing side transceiver apparatus 11 is controlled according tothe transmission level change information transmitted from thetransceiver apparatus 12 added to the data (data B).

Next, an explanation will be made of some examples of the parts (21, 51)for generation of a required reception level mentioned above.

FIG. 5 is a view of a first example for generating a required receptionlevel. Reference numeral 61 is a change-over switch attached to thetransceiver apparatus (11 of FIG. 3 or 12 of FIG. 4). The classificationof the data (data A) is set by the change-over switch 61 beforehand whenthe data to be transmitted is known in advance.

Due to this, the required BER for the data classification and thereception level required for this are also set (34).

By comparing this with the reception level measured at the opposing sidetransceiver apparatus 12 (FIG. 3) (35), it becomes possible to controlthe change of the transmission level (33). Note that reference numeralsin parentheses show the corresponding circuit parts in FIG. 3.

FIG. 6 is a view of a second example for generating a required receptionlevel. As shown in FIG. 6, the change-over switch 62 is attached to thetransceiver apparatus (11 of FIG. 3). The required BER is freely set inadvance by the switch, volume knob, or the like. Due to this, a requiredreception level enough to secure this required BER is generated (34).This and the reception level (36) measured at the opposing side arecompared (35), whereby it becomes possible to control the change of thetransmission level (33) and becomes possible to freely alter the channelquality.

FIG. 7 is a view of a third example for generating a required receptionlevel.

When a personal computer or other terminal is connected to thetransceiver apparatus 11 (FIG. 3) for communication, the dataclassification is switched beforehand by the switch, volume knob, or thelike in the software at the terminal. Then, discrimination bits forallowing discrimination of the data classification are added to framesof the transmission data for transmission to the transceiver apparatus12 (31).

The transceiver apparatus 12 reads the discrimination bits added to theframes of the received data, generates a required reception level enoughto secure the required BER of the data A (34), and compares this and themeasured reception level (43) (35), whereby it becomes possible tocontrol the change of the transmission level (54).

Table 2 is a table for converting the BER represented by a×10^(−b) to6-bit information ABCDEF.

TABLE 2 a ABC b DEF 1.0 000 9 111 2.0 001 8 110 3.0 010 7 101 . . . . .. . . . . . .

FIG. 8 is a view of a fourth example for generating a required receptionlevel.

When a personal computer or other terminal is connected to thetransceiver apparatus 11 (FIG. 4), when transmitting data by thatterminal, the required BER is switched by the change-over switch 64 inadvance in the software of the related computer or the like, therequired BER for the data classification is converted to 6-bit data (thefirst 3 bits of the header representing the multiplier of the BER andthe latter 3 bits representing the absolute value of the exponent)according to Table 2, added to the header of the data frame to betransmitted, and transmitted to the transceiver apparatus 12.

In the transceiver apparatus 12, the information of the added requiredBER is read, and the required reception level capable of securing theBER is generated (34).

FIG. 9 is a view of a fifth example for generating a required receptionlevel.

Reference numeral 71 of the figure is an interface unit provided in thetransceiver apparatus 11 (FIG. 3). The data classification isautomatically discriminated at a data classification discrimination unit72 according to which of the interfaces, different for eachclassification of the data to be transmitted (data A), is active (busy).Then, a required reception level enough to secure the required BER ofthe data classification is generated (34), this and the reception levelat the opposing side receiver (36) are compared (35), and thetransmission is controlled according to the result of the comparison(33).

FIG. 10 is a view of a sixth example for generating a required receptionlevel.

Reference numeral 71 of the figure is an interface unit provided in thetransceiver apparatus 11 (FIG. 3) similar to FIG. 9. Required BERscorresponding to the interfaces, different for the classifications ofthe data to be transmitted (data A), are given by a BER setting unit 73.A reception level for realizing the required BER for the dataclassification of the input data (data A) is generated (34). Thisreception level and the reception level (36) at the opposing sidetransceiver apparatus 12 (FIG. 3) are compared (35), and thetransmission is controlled according to the result of this comparison(33).

FIG. 11 is a view of a seventh example for generating a requiredreception level.

When connecting a personal computer or other terminal to the transceiverapparatus, a driver (for example, a discrimination bit adding unit 76mentioned later) or the like is installed in that computer and extensioncodes of the transmission file are monitored by the software within theterminal at the time of file transfer. The contents of the transmissiondata are discriminated by the extension codes, for example, if theextension code is ______.wav, it is audio data, while if the extensioncode is ______.mpg, it is a moving picture. This is done by an extensioncode discriminating unit 75. The result of the discrimination is addedto the header of the frame of the transmission data (data A) as thediscrimination bits. This is done by a data classificationdiscrimination bit adding unit 76. This is further transmitted to thetransceiver apparatus.

In the transceiver apparatus, the added discrimination bits are read, arequired reception level enough to secure the required BER of that datais generated (34), this required reception level and the reception level(36) at the opposing side transceiver apparatus are compared (35), andthe transmission is controlled according to the result of the comparison(33).

FIG. 12 is a view of an eighth example for generating a requiredreception level.

When connecting a personal computer or other terminal to the transceiverapparatus, a driver (for example, a discrimination bit adding unit 77mentioned later) or the like is installed in that computer and extensioncodes of the transmission file are monitored by the software within theterminal at the time of file transfer. The contents of the transmissiondata are discriminated by the extension codes as mentioned above, forexample, if the extension code is ______.wav, it is audio data, while ifthe extension code is ______.mpg, it is a moving picture. This is doneby the extension code discriminating unit 75. Then, the required BERaccording to the data belonging to the extension code is converted tothe 6-bit data according to Table 2, added to the header of the frame ofthe transmission data as the BER information, and transmitted to theopposing side transceiver apparatus. This is done by a dataclassification discrimination bit adding unit 77.

In the transceiver apparatus, a required reception level capable ofsecuring the required BER indicated by the added BER information isgenerated (34), the required reception level and the reception level atthe opposing side transceiver apparatus (36) are compared (35), and thetransmission is controlled according to the result of the comparison(33).

FIG. 13 is a view for explaining adjustment in the case of generatingthe required reception level. This is a procedure for individuallyadjusting the required BER according to the situation in the wirelesslocal loop system.

In FIG. 13, when the classification of the data is discriminated, apredetermined BER (required BER) is allocated in accordance with theclassification such as video, teletext broadcast, or other data. Here,the required BER can be individually adjusted. In the figure, an up/downswitch 79 is shown as an example of the means for adjustment. Whentaking as an example video data, 3.0×10⁻⁹ can be adjusted to for example4.0×10⁻⁹ (up) or 2.0×10⁻⁹ (down). It is possible to perform thistogether for all required BER and also possible to perform this for onlyaudio data. How is this adjusted may be suitably determined by the useraccording to the system status.

Summarizing the effects of the invention, almost all of the methods oftransmission level control of the related art monitored the opposingside reception level, BER, etc. to realize control of the requiredlowest limit of the transmission level. In this case, when theclassification of the transmission data is fixed, the required C/N isalso fixed, so there is no problem, but when it is intended to transmita variety of data having different required C/Ns and BERs, the lines aredesigned to match with the strictest required C/N and the transmissionlevel determined accordingly, so when transmitting data not having astrict required C/N, the transmission is carried out with an excessiveoutput.

In order to solve this problem, the present invention enables thetransmission level to be flexibly controlled on the same channel byreferring to the opposing side reception level and further referring tothe required C/N and reception level according to the classification ofthe transmission data—without distinguishing the continuity ordiscontinuity of the data (packet, cell, etc.). By this, the powerconsumption can be lowered, and the interference to other channels canbe reduced while making it possible to secure a sufficient channelquality.

While the invention has been described with reference to specificembodiments chosen for purposes of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

1. A transceiver apparatus, comprising: a setting unit when a radio signal to be received includes a first data, specifying a first error rate required for the first data, generating information of a first reference quality so as to satisfy the specified first error rate, and setting the generated information of the first reference quality as a reference radio quality, said setting unit, when a radio signal to be received includes a second data, specifying a second error rate required for the second data, generating information of a second reference quality so as to satisfy the specified second error rate and setting the generated information of the second reference quality as a reference radio quality; a comparison unit for comparing the reference radio quality set by said setting unit with a radio quality of a received signal; a transmitting unit for transmitting, to an opposing transceiver, a signal for a control of a transmission power to be produced in said opposing transceiver apparatus depending on the result of the comparison by said comparison unit; and an adjusting unit being able to adjust the first error rate and the second error rate, individually. 